Many different processes and composttions have been proposed for chemically reducing ammonia levels in an effluent, including catalytic and non-catalytic processes as well as thermal processes. Typical of catalytic processes is that disclosed by Kimura et al. in U.S. Pat. No. 4,233,275. The Kimura et al. process involves the decomposition of ammonia by a reduced iron catalyst in a process for purifying a high pressure raw coal gas. In a somewhat similar non-catalytic process, Dean, in U.S. Pat. No. 4,423,017, teaches the decomposition of ammonia in a combustion eflluent by contacting the effluent with a metallic material such as iron-, nickel- and cobalt-based alloys, within a gas residence time zone of less than one second from the ammonia source.
Azuhata et al. disclose another non-catalytic process for the decomposition of ammonia in U.S. Pat. No. 4,213,944 by teaching the addition of hydrogen peroxide to a combustion effluent to which ammonia is added to reduce the nitrogen oxides concentration of the effluent.
Representative of thermal processes for ammonia decomposition are those disclosed by Palm et al. in U.S. Pat. No. 4,391,790 and McGill et al. in U.S. Pat. No. 4,519,993. Palm et al. disclose the decomposition of ammonium compounds deposited on a catalyst are removed by passing a regeneration stream in contact with the catalyst for produce an ammonia containing regeneration stream and combusting the regeneration stream at high temperatures (i.e., 2400.degree. F. to 2600.degree. F.). McGill et al. disclose a process wherein an effluent is contacted with an effective amount of oxygen containing gas and a stoichiometric amount of a hydrocarbon at a temperature of greater than 2000.degree. F. to decompose ammonia.
Tenner et al., in U.S. Pat. No. 4,115,515, disclose the reduction of nitrogen oxides by injecting ammonia, with or without an additional reducing composition. In a specific embodiment of Tenner et al., ammonia is introduced into the effluent at 900.degree. to 1000.degree. C. to reduce nitrogen oxides in the effluent and hydrogen is injected into the effluent at 700.degree. to 900.degree. C. to combine with "unconverted" ammonia to maximize the NO.sub.x reductions achievable with the Tenner et al. process.
What is needed is a non-catalytic process for substantially reducing the concentration of ammonia in an effluent, preferably as an adjunct to a process for reducing the concentration of nitrogen oxides in the effluent.